Theoretically, single-walled carbon nanotube field-effect transistors (SWNT FETs) are predicted to have intrinsic cut-off frequencies approaching the THz range, where intrinsic means that the parasitic capacitance due to fringing fields is negligible compared to the gate-source capacitance required to modulate the conductance. However, in real world applications, this parasitic capacitance tends to dominate most CNT FET geometries.
When fabricating an individual CNT FET, it would beneficial to be able to measure its full S-parameters (or equivalently Z, h, or ABCD matrix), and then come up with an equivalent circuit model that could then be compared to theoretical models and used as basis to construct more complex circuits out of more than one CNT FET. However, in practice, the high impedance and low on current of a single CNT FET have served to hinder prior attempts to obtain these measurements.